DE133729C - - Google Patents

Description

IMPERIAL

PATENT OFFICE

The procedure described below was worked out on the basis of the observation that that the metallic silver in a thin layer when it comes out of the solution of its resinate is reduced by heating under suitable circumstances, an unusually large hiding power and high reflectivity, two qualities that still come into play even when between the reduced silver particles contain oxides of other metals in considerable quantities will.

While with bright gold 10 to 12 pCt. metallic gold are required to look after to obtain a well-covering metal layer on porcelain and the like after baking, a content of 1.5 to 3 pCt is sufficient. on metallic silver one with bismuth resinate solution offset and coated with approximately the same layer thickness of silver resinate solution completely covering metal layers when stoving according to the presently protected process from silver to platinum sheen.

This makes it possible to use a cheap way of making ceramic objects metallic to make shiny or to gain shiny metal preparations, which in comparison to the common ones due to their low content of expensive precious metals (gold, platinum, etc.) to distinguish oneself.

The exploitation of this possibility has hitherto stood in the way of reducing it Silver is not fire-resistant when stoved in the usual way, but in ordinary ways Muffle fire partly due to oxidation, partly due to molecular change in the eye is made invisible.

In order to work out a useful procedure on the basis of the facts presented here, The first task to be solved was the following:

1. To hold on to the silver sheen that disappears when heated.

2. For the purpose of imitating yellow or yellow-green or red reflecting metals or Alloys the silver luster without considerable expenditure of precious metal by suitable additives to change, i.e. to find mixtures which meet the above requirement.

3. To design the coatings in such a way that they adhere sufficiently firmly to the substrate.

All these requirements can be met by using of the preparations described below from the usual method of baking in muffle furnaces at Rothglut and use a suitable one for each individual preparation, but for all preparations keeps the temperature between the not too wide limits of 340 to 480 ° C.

A.

A preparation for silver to platinum luster is obtained by mixing 1 5 parts of bismuth resinate solution (with 5.35 pCt. Bi. ₂ O ₃ ), 100 parts.

Silver solution (3.4 perc.) Prepared according to patent 113170, 4 th. Boric acid solution in benzyl alcohol (as indicated under B ).

The preparation is used at a temperature of 360-380 ⁰ C.. At a temperature of over 400 ^° C. the silver coating burns, it becomes dull and unusable. The addition of commercially available bright gold or bright platinum to this preparation makes the reduced silver resistant to the action of hydrogen sulphide, and it can then be used at a somewhat higher temperature. It is true that mixtures of resinous silver and resinous bismuth have already been baked onto glass in order to achieve shiny metallic coatings. The result is the well-known silver chandelier, which only works on types of glass with a certain composition or on soft glazes, and is then also extremely unsafe (D in gier's polytechn. Journal, vol. 266, p. 366, paragraph 3, lines 10 to 13). The effect is a completely different one, in that these lustres allow yellow light to pass through, i.e. not cover it (cf. Dingler's polytechn. Journal, vol. 266, p. 364, line 8 to).

But the invention rests precisely in the knowledge that one adheres to certain Coats that cover temperatures even with dilute solutions are obtained.

Technically, the two processes are quite different: there the silver is completely Oxidation and heated until it penetrates the glass surface and subsequently reduced again by fire gases and so on (p. 366 above paper, lines 1 to 4); here the oxidation is determined by observance Temperatures avoided from the outset.

According to the old method, solutions of the metal in the glass substance are obtained, according to the new, on the other hand, coatings which have not penetrated into the substrate, but rather lying on the same, are held by adhesion. Both are different also through their behavior towards nitric acid.

The regulation for the representation of the shiny silver in Strele's manual of porcelain and stained glass, p. 81, is one of those useless Receipts which in great numbers flood technical literature; even is made from lavender oil and silver nitrate at that point even before the shiny silver is applied warned. Such a mixture could only then be used for normal muffle fires if it contained much silver, in which case a part of the silver would be present Oxidation remains protected.

B.

If one mixes pure gold and silver sulfur resin solutions in essential oils, it shows a predominance of the silver sheen. The mixture burns at the ratio:

ι Th. Au: ι Th. Ag silvery white, 3 ■ - -: ι - - pale yellowish white, 6 - -: ι - - light yellow.

The color of gold comes especially when a solution of less than 6 pCt. in applied to the mixture is hardly effective. On the other hand, one changes a lot a small addition of silver to the concentrated gold solution changes the color of the gold, it tones it more against weifs (against light gold, as the painters put it). This is also how the silver content serves in certain bright gold preparations which are found in the trade and which contain gold, silver and bismuth, only for tinting them achieved bright gold plating. By the way, these preparations are common as they are in Way to be burned in with weak red embers, for use in shape high percentage solutions determined. But if you fire solutions of gold, silver and Bismuth sulfur resin solutions according to the present process at low temperatures, in this way there is again the possibility of using considerably less than the usual stoving Content of the precious metal solutions used, provided that they are spread equally thick, to obtain glossy metal coatings with good coverage. It is also shown that under under these circumstances and if the mixing ratios given below are observed Gold, the color of the silver-gold plating obtained has a much stronger yellow tint than the known ones Preparations to be burned in with red embers. · 'So one obtains with mixtures of gold, Silver and bismuth solutions in the ratio:

6 Th. Au : 1 Th. Ag: 4 to 6 Th. BL ₂ O ₃ after stoving well covering layers of bronze luster,: 3 "- - - - - - ■ ■ - -. Yellow luster,

: 2 - - - - - - - - - yellow-green

Gold luster,: ι-- - - - - - - greenish

Metallic luster.

3 - ■ -

ι -

The gold content can always be below 6 pCt. being held; usually a content of 2.5 to 5 pCt is sufficient. in order to obtain sufficient covering layers, in contrast to the bright gold previously used in ceramic gold plating, where a gold content of at least .9 to ι ο pCt. is required. In particular, the ratio 2.5 to 4 Th. Au : 1 Th. Ag ' draws "

is made up of the fact that an increase in the bismuth content of less than 4 pCt. Au can still obtain well-covering layers of brass or glitter gold luster.

By changing the mixing ratios and adding other metal oxides, achieve varied color changes.

Addition of boric acid to benzyl alcohol (1 B (OH) _S , to 10 benzyl alcohol and boiling until the water is completely driven off) increases the strength and tones the color more against yellow. 3 to 10 parts of this solution are added to 100 parts of the above mixture.

The temperature also has an influence on the color. So obtained a mixture which 3.5 pCt. Au, 1.18 pCt. Ag and 2.7 pCt. Bi ₂ O _3, at 360 ⁰ C. grüngoldigen gloss, at 440 ° C. but more the color of tinsel. At a temperature of more than 480 ° C, that is, far below a dark red glow, the coating burns and is then mifs-colored and unusable. The temperature determinations are based on the Heraeus pyrometer.

Instead of bismuth oxide, other oxides can also be used, but they usually give less beautiful effects.

Application of the preparations.

The preparations described here can be used like ordinary bright gold or like luster colors be applied to the objects to be decorated. On the other hand, it is completely different the type of burn-in.

While so far the painted clay ware and so on have always been burned with glowing heat, a temperature between narrow limits must be maintained here.

The low temperature leads to a simplification of the operation by the fact that most commodities can be put into the required quantities immediately, without prior heating Can bring temperature to heated room and only leave there for a short time (until the reduction the metals), whereupon they can be transferred to the refrigerator.

By eliminating the preheating and the glow temperature, there is also a saving of fuel brought about, furthermore the possibility of using the fire gases of other companies expediently to take advantage of.

Under these circumstances, it is possible, without increasing the operating costs, of the hitherto customary process of baking ceramic colors deviate by one no longer has to store the goods to be burned in as narrow a space as possible stratified to expose one another to the embers, which always leads to overheating of individual parts led. One can rather have the goods individually or lying next to each other, for example on one wide ribbon without end, feed it into the oven, making the same much faster and be heated more evenly to the required temperature.

Even base metals (e.g. iron), even superficially oxidized, can use this Process can be provided with metallic luster without it being necessary to apply the oxide layer beforehand to be removed (which is absolutely necessary for galvanic gold plating). Although the metal layer adheres very firmly to the base, it offers no protection against Subsequent rusting should therefore only be applied where subsequent oxidation is not to be feared is.

Enamelled sheet iron and the like can also be given a metallic sheen.

Claims (2)

Patent-to sayings: 1. Process for the production of opaque, metal-shining coatings on glass, ceramic objects, enamels, base metals, "by means of baking of solutions of organic silver and bismuth - or of silver, bismuth and gold compounds, characterized in that the baking is carried out at a temperature lying between 340 and 480 ^{0 C.} 2. An embodiment of the method characterized in claim 1, in which - · to achieve a green-yellow or yellow metallic luster - the metal-sulfur resin solutions on ι Th. Silver (Ag) 2.5 to 6 Th. Gold (Au) and 2 to 4.5 Th. Contains bismuth oxide (Bi ₂ O ₃ ) .